Octopus Trivia
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95 free Octopus trivia questions with answers — nature quiz, new questions added Oct 2026.
This octopus trivia quiz covers the ocean's strangest and smartest invertebrate. The easy questions handle the basics: how many arms and hearts it has, what colour its blood is, what it squirts at predators, how it changes colour and how long it lives. The harder end goes deeper: why two-thirds of its neurons live in its arms, the copper protein that makes its blood blue, the hectocotylus arm and the grim end that follows mating, the giant Pacific octopus and its 180,000 eggs, the tetrodotoxin of the blue-ringed octopus, coconut-carrying veined octopuses, the dumbo octopus photographed 6,957 metres down, the octopus plural argument, Hokusai's infamous print, and Paul, who picked World Cup winners. Every answer was checked against the encyclopaedia entry before publishing and the supporting sentence is stored with each question. Our ocean, sea creatures and animal quizzes are the natural next stop.
30 of 95 questions with answers and explanations. Play the quiz
Q 01To which class of molluscs do octopuses belong, along with squid, cuttlefish and nautiluses?
Cephalopoda
Cephalopoda is the mollusc class of octopuses, squid, cuttlefish and nautiluses; apart from the nautiluses, its living members have tucked the ancestral shell inside the body or lost it altogether.
Q 02How many hearts does an octopus have?
Three
An octopus has three hearts: two branchial hearts push blood through the gills and one systemic heart sends it round the body, which keeps the pressure high enough to move its thick blood.
Q 03Which copper-based protein carries oxygen in octopus blood?
Haemocyanin
Haemocyanin carries oxygen on copper where our haemoglobin uses iron, and it does the job better than haemoglobin in cold, low-oxygen water, which suits life in the ocean.
Q 04What fraction of an octopus's neurons are located in its arms rather than its brain?
Two-thirds
About two-thirds of an octopus's neurons lie in its arms rather than its central brain, which is why a severed arm can keep moving and reacting to touch for a while.
Q 05Which is the only kind of octopus known to be deadly to humans?
Blue-ringed
Blue-ringed octopuses, genus Hapalochlaena, are the only octopuses known to have killed people; every octopus is venomous, but no antivenom exists for a blue-ringed bite.
Q 06Which toxin, also the poison of pufferfish, lets the deadliest octopus paralyse its victims?
Tetrodotoxin
Tetrodotoxin, made by bacteria in the octopus's salivary glands, blocks the sodium channels that nerves need to fire; victims kept breathing by machine through the first day usually recover fully.
Q 07Which species is usually cited as the largest octopus?
Giant Pacific
The giant Pacific octopus is the species usually called the largest, with an arm span that often passes 4 metres, yet it hatches from an egg the size of a grain of rice.
Q 08Which octopus, weighing under a gram as an adult, is the smallest known species?
Star-sucker pygmy
The star-sucker pygmy octopus of the western Pacific is small enough to sit on a fingertip; as its name suggests, males carry fringed, star-shaped suckers.
Q 09An octopus is said to squeeze through any hole no smaller than which part of its body?
Its beak
Its beak, a parrot-like bill, is often said to be the limit: it is the only hard part of an octopus, and the rest is boneless soft tissue that can pour through a gap after it.
Q 10Georges Cuvier mistook a detached mating arm of a male octopus for what?
A parasitic worm
A parasitic worm, he decided, and named it Hectocotylus as a new species; the name stuck to the arm after Japetus Steenstrup showed in 1856 that males use it to pass sperm.
Q 11What happens to a male octopus after mating?
He becomes senescent and dies
He becomes senescent and dies: after mating, a male octopus stops eating, weakens and is dead within a few months, while the female dies after brooding her eggs.
Q 12Which deep-sea animal with eight webbed arms is the octopuses' closest living relative?
The vampire squid
The vampire squid is neither a squid nor a blood-drinker: it shares the superorder Octopodiformes with the octopuses and feeds on 'marine snow', the debris drifting down from the waters above.
Q 13How long does a common octopus usually live?
One to two years
Q 21What extra sense do an octopus's suckers give its arms?
Taste whatever it touches
Chemoreceptors in the suckers let an octopus taste whatever it touches; a chemical in its own skin switches off the suckers' grip, which is what stops its arms sticking to one another.
Q 22Which organs in an octopus's head detect gravity and acceleration, and possibly sound?
Statocysts
Statocysts are paired sacs in which a tiny stone rests on sensory hairs, so its shifting weight signals gravity and acceleration; with them the common octopus can also detect sounds of roughly 400 to 1,000 Hz.
Q 23Octopuses sometimes hunt cooperatively with fish, and keep their partners in line by doing what?
Punching them
One to two years is the usual lifespan of a common octopus, and even the biggest species manage about five; yet one deep-sea mother off California was watched guarding a single clutch of eggs for 53 months.
Q 14Removing which glands lets a brooding female octopus start eating again and live much longer?
The optic glands
The optic glands release the signals behind a mother octopus's fatal fast; in Jerome Wodinsky's 1977 experiment, females without them stopped brooding, fed again and lived far longer.
Q 15What is the main pigment in octopus ink?
Melanin
Melanin, the same pigment that darkens human skin and hair, is the main pigment in octopus ink; the ink mixes with mucus and leaves the funnel as a dark blob that works as a decoy or smokescreen.
Q 16Which specialised skin cells give an octopus its rapid camouflage?
Chromatophores
Chromatophores are elastic pigment sacs in the skin, holding yellow, orange, red, brown or black, that muscles stretch open or shut in an instant; iridophores and leucophores beneath add shimmer and white.
Q 17What is the octopus display called in which waves of dark colour ripple across the body?
The passing cloud
The passing cloud is a dark wave that sweeps over the body and arms like a cloud's shadow; octopuses often show it when a hunted crab freezes, so it is thought to startle prey into moving.
Q 18When damselfish attack it, the mimic octopus has been seen impersonating which of their predators?
A sea snake
A sea snake, banded and venomous, is the disguise it picks for damselfish; the mimic octopus, discovered in Indonesia in 1998, also poses as lionfish and sole, apparently matching the act to the threat.
Q 19The veined octopus is famous for collecting and carrying what to build a shelter?
Discarded coconut shells
Discarded coconut shells are dug up, rinsed with jets of water and carried off under the body in an awkward 'stilt walk', then put back together as a shelter when needed: a celebrated case of tool use.
Q 20What is an octopus's fastest way of moving?
Jet propulsion
Jet propulsion shoots water from the mantle out through the funnel to rocket the octopus away; it is costly, so octopuses save it for escapes and mostly crawl.
Punching them: a day octopus whips out one arm in an explosive jab that knocks a fish out of position, and a 2024 study found blacktip groupers, which hang back and freeload, took the most hits.
Q 24Unlike nearly all other octopuses, the larger Pacific striped octopus has been found doing what?
Living in groups
Living in groups of up to 40, in dens about a metre apart, was reported by Arcadio Rodaniche decades ago; a team confirmed much of the account only after keeping live animals from 2012.
Q 25As of a 2020 study, which octopus is the deepest ever filmed, nearly 7,000 metres down in the Indian Ocean?
Dumbo
Dumbo octopuses took the record when a camera lander caught one 6,957 metres down in the Java Trench, a sighting that suggests cephalopods could live on about 99% of the world's seafloor.
Q 26The dumbo octopus is named for which body part, which resembles the ears of Disney's flying elephant?
Its fins
Its fins, one on each side of the mantle above the eyes, flap to row the dumbo along; cirrate octopuses like it swim this way and usually have no ink sac.
Q 27Which habitat has no known octopus species at all?
Fresh water
Fresh water has no octopus, nor any other cephalopod; yet octopuses live in the frigid seas off Antarctica and one species, Vulcanoctopus hydrothermalis, beside deep hydrothermal vents.
Q 28The female argonaut, an open-ocean octopus, rides in a thin white 'shell' that is really what?
A secreted egg case
The argonaut's 'shell' is a secreted egg case: the female makes it herself, broods her eggs inside and gulps air into it at the surface to control her buoyancy.
Q 29Which plural treats 'octopus' as a Latin word, though it actually comes from Greek?
Octopi
Octopi copies Latin plurals such as cacti, but octopus comes from Greek, where the plural would be octopodes; dictionaries accept octopi anyway, though octopuses is the more common form.
Q 30The word 'octopus' comes from Greek words meaning what?
Eight foot
Eight foot is the literal sense of the Greek oktopous, from okto, eight, and pous, foot; the same pous ends platypus, 'flat-footed', which is why the two animals share half a name.